POS0280 EARLY EXPERIENCE WITH JAK INHIBITORS IN JIA IN ROUTINE CLINICAL PRACTICE
Authors: L. Kearsley-Fleet, E. Baildam, M. Beresford, S. Douglas, H. Foster, T. Southwood, K. Hyrich
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> For the past 20 years, biologic (b)DMARDs have been the main treatment option for children and young people with JIA where an initial conventional-synthetic DMARD has not been effective. Since 2021, tofacitinib, a Janus Kinase (JAK) inhibitor has become available for the treatment of JIA. In the phase 3 randomised controlled withdrawal design trial, tofacitinib demonstrated superior efficacy over placebo, although only 38% of patients had prior bDMARD exposure. There is little information on the use of JAK inhibitor in the real-world. <h3>Objectives</h3> This analysis aims to describe the early experience of children and young people with JIA in a real-world cohort receiving JAK inhibitor in the United Kingdom (UK). <h3>Methods</h3> All patients in the UK JIA Biologics Register starting a JAK inhibitor were identified. Patient characteristics are presented at the time of treatment start, including age, disease duration and prior bDMARDs. Patients were followed until their latest follow-up form was returned. Active joint count (AJC) was reported at start of therapy and after 6 months. Status at their last follow-up was reported including treatment persistence. <h3>Results</h3> As of 21-Nov-2022, 14 children and young people across most ILAR categories had been treated with a JAK inhibitor; 12 baricitinib, 2 tofacitinib (table 1). Median age at JAK inhibitor start was 16 years (interquartile range [IQR] 13-17) and median disease duration was 6 years (IQR 4-7). All patients had prior bDMARD exposure, with 12 out of the 14 having more than 2 prior bDMARDs (range 2-6). Ten patients had follow-up available after the start of JAK inhibitor (median 1.4 years of follow-up available; median 0.8 years on treatment available). At the latest follow-up, 6 patients remained on JAK inhibitor, whilst 4 patients had discontinued (3 for ineffectiveness). No venothromboembolism (VTE) have been reported. In eight patients who had disease activity data available at the start of treatment, median active AJC was 9 (IQR 5-25). In the six patients who had disease activity data available after 6 months of JAK inhibitor treatment, median AJC was 2 (IQR 0-4). <h3>Conclusion</h3> In this cohort, the initial patients with JIA prescribed JAK inhibitor have largely received these drugs prior to marketing authorisation in JIA, with most receiving it as a later stage biologic/targeted-synthetic DMARD. Most patients were still receiving treatment almost 11 months after starting a JAK inhibitor. These data suggest that JAK inhibitors could be a very effective treatment for children and young people with JIA, even after a high number of prior bDMARDs. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Lianne Kearsley-Fleet: None declared, Eileen Baildam: None declared, Michael Beresford: None declared, Sharon Douglas: None declared, Helen Foster: None declared, Taunton Southwood: None declared, Kimme Hyrich Speakers bureau: Non-personal speaker's fees from Abbvie, all unrelated to this abstract., Grant/research support from: Grant income from BMS, UCB, and Pfizer, all unrelated to this abstract, and is supported by the NIHR Manchester Biomedical Research Centre.